diff --git a/dom/base/test/jsmodules/test_syntaxError.html b/dom/base/test/jsmodules/test_syntaxError.html
index 53f95c96cc..5bd688fe3f 100644
--- a/dom/base/test/jsmodules/test_syntaxError.html
+++ b/dom/base/test/jsmodules/test_syntaxError.html
@@ -4,20 +4,27 @@
 <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
 <script>
   var wasRun = false;
-  var hadSyntaxError = false;
+  var errorCount = 0;
+  var syntaxErrorCount = 0;
+  var eventCount = 0;
 
   SimpleTest.waitForExplicitFinish();
   window.onerror = handleError;
 
   function handleError(message, url, line, column, error) {
-    hadSyntaxError = error instanceof SyntaxError;
+    errorCount++;
+    if (error instanceof SyntaxError) {
+      syntaxErrorCount++;
+    }
   }
 
   function testError() {
     ok(!wasRun, 'Check script was not run');
-    ok(hadSyntaxError, 'Check that a SyntaxError was thrown');
+    ok(errorCount == 1, 'Check that an error was reported');
+    ok(syntaxErrorCount == 1, 'Check that a syntax error was reported');
+    ok(eventCount == 0, 'Check that no error event was fired');
     SimpleTest.finish();
   }
 </script>
-<script type="module" src="module_badSyntax.js"></script>
+<script type="module" src="module_badSyntax.js" onerror="eventCount++"></script>
 <body onload='testError()'></body>
diff --git a/dom/base/test/jsmodules/test_syntaxErrorAsync.html b/dom/base/test/jsmodules/test_syntaxErrorAsync.html
index 35d9237553..3593d9dd73 100644
--- a/dom/base/test/jsmodules/test_syntaxErrorAsync.html
+++ b/dom/base/test/jsmodules/test_syntaxErrorAsync.html
@@ -4,20 +4,27 @@
 <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
 <script>
   var wasRun = false;
-  var hadSyntaxError = false;
+  var errorCount = 0;
+  var syntaxErrorCount = 0;
+  var eventCount = 0;
 
   SimpleTest.waitForExplicitFinish();
   window.onerror = handleError;
 
   function handleError(message, url, line, column, error) {
-    hadSyntaxError = error instanceof SyntaxError;
+    errorCount++;
+    if (error instanceof SyntaxError) {
+      syntaxErrorCount++;
+    }
   }
 
   function testError() {
     ok(!wasRun, 'Check script was not run');
-    ok(hadSyntaxError, 'Check that a SyntaxError was thrown');
+    ok(errorCount == 1, 'Check that an error was reported');
+    ok(syntaxErrorCount == 1, 'Check that a syntax error was reported');
+    ok(eventCount == 0, 'Check that no error event was fired');
     SimpleTest.finish();
   }
 </script>
-<script type="module" src="module_badSyntax.js" async></script>
+<script type="module" src="module_badSyntax.js" async onerror="eventCount++"></script>
 <body onload='testError()'></body>
diff --git a/dom/base/test/jsmodules/test_syntaxErrorInline.html b/dom/base/test/jsmodules/test_syntaxErrorInline.html
index 705bc5902e..b85b954ece 100644
--- a/dom/base/test/jsmodules/test_syntaxErrorInline.html
+++ b/dom/base/test/jsmodules/test_syntaxErrorInline.html
@@ -4,22 +4,29 @@
 <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
 <script>
   var wasRun = false;
-  var hadSyntaxError = false;
+  var errorCount = 0;
+  var syntaxErrorCount = 0;
+  var eventCount = 0;
 
   SimpleTest.waitForExplicitFinish();
   window.onerror = handleError;
 
   function handleError(message, url, line, column, error) {
-    hadSyntaxError = error instanceof SyntaxError;
+    errorCount++;
+    if (error instanceof SyntaxError) {
+      syntaxErrorCount++;
+    }
   }
 
   function testError() {
     ok(!wasRun, 'Check script was not run');
-    ok(hadSyntaxError, 'Check that a SyntaxError was thrown');
+    ok(errorCount == 1, 'Check that an error was reported');
+    ok(syntaxErrorCount == 1, 'Check that a syntax error was reported');
+    ok(eventCount == 0, 'Check that no error event was fired');
     SimpleTest.finish();
   }
 </script>
-<script type="module">
+<script type="module" onerror="eventCount++">
 // Module with a syntax error.
 some invalid js syntax;
 wasRun = true;
diff --git a/dom/base/test/jsmodules/test_syntaxErrorInlineAsync.html b/dom/base/test/jsmodules/test_syntaxErrorInlineAsync.html
index 5e79928234..cc4bf12575 100644
--- a/dom/base/test/jsmodules/test_syntaxErrorInlineAsync.html
+++ b/dom/base/test/jsmodules/test_syntaxErrorInlineAsync.html
@@ -4,22 +4,29 @@
 <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
 <script>
   var wasRun = false;
-  var hadSyntaxError = false;
+  var errorCount = 0;
+  var syntaxErrorCount = 0;
+  var eventCount = 0;
 
   SimpleTest.waitForExplicitFinish();
   window.onerror = handleError;
 
   function handleError(message, url, line, column, error) {
-    hadSyntaxError = error instanceof SyntaxError;
+    errorCount++;
+    if (error instanceof SyntaxError) {
+      syntaxErrorCount++;
+    }
   }
 
   function testError() {
     ok(!wasRun, 'Check script was not run');
-    ok(hadSyntaxError, 'Check that a SyntaxError was thrown');
+    ok(errorCount == 1, 'Check that an error was reported');
+    ok(syntaxErrorCount == 1, 'Check that a syntax error was reported');
+    ok(eventCount == 0, 'Check that no error event was fired');
     SimpleTest.finish();
   }
 </script>
-<script type="module" async>
+<script type="module" async onerror="eventCount++">
 // Module with a syntax error.
 some invalid js syntax;
 wasRun = true;
